Method of manufacturing composite board

ABSTRACT

A composite board is made from waste medium density fiber (MDF) board or waste particle board that includes solid urea formaldehyde. The waste board is chopped and milled into particles having a size between 20 mesh and 150 mesh, creating a waste flour. After removing moisture from the waste flour, the dried waste flour is mixed with a thermoplastic to bind and encapsulate the waste flour. Internal lubricants are added to improve the flow characteristics of the blended material, and external lubricants are added to present sticking of the mixture to an extruder or mold. Mineral fillers are added to improve the flexural modules of the composite board, and a plasticizer can be added to improve the physical properties or mechanical characteristics of the mixture. An ultraviolet absorber, a biocide, and a pigment can also be added. The blended material is extruded or molded into a desired shape. When cooled, the thermoplastic hardens to form a solid composite board.

BACKGROUND OF THE INVENTION

[0001] The present invention relates generally to a method ofmanufacturing composite board from waste materials including solid ureaformaldehyde.

[0002] Man made composite boards are made from wood and have thefeatures of natural wood. When manufacturing composite boards, such asmedium density fiber (MDF) boards or particle boards, wood is firstground into wood chips of a desired size. In one prior art compositeboard, the wood chips are then mixed with liquid urea formaldehyde in ablender until uniformly blended. Urea formaldehyde is a thermosetplastic. The homogenized mixture is then extruded or molded into adesired shape. The urea formaldehyde cross-links in the mixture,hardening and solidifying the composite board. The composite board canbe coated with polyvinyl chloride (PVC), melamine, metal, foil,impregnated paper, wood veneer that is stained and sealed or polyesterto make the composite board decorative and wear resistant and to provideother properties. The hardened composite board is then cut to a desiredshape and size, and then further processed by cutting, drilling, oredging to create a component part. The composite boards can be used ascabinets, molding, storage units, desks, or other products.

[0003] When composite boards including urea formaldehyde are discarded,they are usually thrown away or burnt and not recycled. In recent years,recycling has become of increased importance due to limited landfillcapacity and an increase in environmental awareness. If the compositeboard is burnt, harmful gases are released into the atmosphere. Adrawback to the prior art composite board is that the discardedcomposite boards are not recycled, increasing the amount of materialcollected and discarded in landfills and the amount of pollutionreleased into the atmosphere.

[0004] Hence, there is need in the art for a method of manufacturingcomposite board from waste material board including solid ureaformaldehyde.

SUMMARY OF THE INVENTION

[0005] The composite board of the present invention is made from wastematerial, such as medium density fiber (MDF) board or particle board,that includes solid urea formaldehyde and other impurities. The wastematerial is chopped into particles approximately one inch in size. Thechopped particles are then ground into smaller particles having a sizebetween ⅛ of an inch and ¼ of an inch. The ground particles are thenmilled into smaller particles having a size between 150 mesh and 20mesh. The urea formaldehyde is in the solid state in the waste MDFboard, and therefore the wood reducing process also chops the ureaformaldehyde into smaller particles of solid urea formaldehyde. Theimpurities are also chopped into smaller particles. Sawdust waste isalso created by the wood reducing process, combining with the milledparticles to form waste flour. After reducing the size of the wastematerial particles, a dryer removes moisture from the waste flour toreduce the moisture content of the waste flour to less than one half of1%.

[0006] The dried waste flour is then added to a blender and mixed withother materials to form a homogeneous mixture. Thermoplastic is added tobind and encapsulate the waste flour. Internal lubricants are added toimprove the flow characteristics of the blended material, and externallubricants are added to prevent the blended material from sticking to anextruder or mold. Mineral fillers are also added to increase theflexural modulus of the finished product and to fill in the voidsbetween the waste flour particles. A plasticizer can also be added toimprove the physical properties or mechanical characteristics of themixture. An ultraviolet absorber, a biocide, and a pigment can also beadded.

[0007] Preferably, the uniformly blended material includes approximately40-70% waste flour, approximately 30-50% thermoplastic, approximately1-3% lubricants, approximately 3-12% mineral fillers, and approximately0.05-3% plasticizers, ultraviolet absorber, biocide, and pigment.

[0008] After thorough mixing, the blended material is extruded or moldedinto a desired shape. The thermoplastic in the mixture cools and hardensto solidify the composite board. The composite board is then cut ormachined to a desired size and shape.

[0009] These and other features of the present invention will be bestunderstood from the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The various features and advantages of the invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiment. The drawings thataccompany the detailed description can be briefly described as follows:

[0011]FIG. 1 schematically illustrates a prior art method of forming amedium density fiber (MDF) board or particle board; and

[0012]FIG. 2 schematically illustrates a diagram of an assembly formanufacturing the composite board of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0013]FIG. 1 schematically illustrates a prior art method ofmanufacturing a medium density fiber (MDF) board or particle board 34.Wood 20 is first ground into wood chips of a desired size in a woodreducer 22. After grinding, the wood chips are mixed with liquid ureaformaldehyde 26 in a blender 28 to form a uniform mixture. Ureaformaldehyde is a thermoset resin. The homogenized mixture is thenmolded or extruded 30 into a desired shape. The urea formaldehydecross-links in the mixture, hardening the mixture into a solid board.The board can then be coated 36 with polyvinyl chloride (PVC), melamine,metal, foil, impregnated paper, wood veneer that is stained and sealed,or polyester to make the board 34 decorative and wear resistant and toprovide other properties. The board is then cut to a desired shape andsize in a sizer 32. The board 34 includes approximately 8-15% ureaformaldehyde by weight. The board 34 can be used as cabinets, molding,deck boards, storage units, desks, or any other product.

[0014] When the board 34 is no longer to be used, the waste board 34 isused to create the composite board 72 of the present invention, ratherthan being discarded and thrown away or burned.

[0015]FIG. 2 schematically illustrates an assembly 38 for manufacturingthe composite board 72 of the present invention. The waste board 34 ischopped in a hog 36 into chopped particles having a size ofapproximately one inch. During chopping, sawdust waste of differentsizes is created. The hog 36 also chops the coating 32 (shown in FIG. 1)applied on the board 34, creating impurities. After chopping, thechopped particles and the sawdust waste 24 are stored in a silo 38 untilneeded.

[0016] The one inch particles are then milled by a first wood reducer 40to form smaller particles having a size between ⅛ of an inch and ¼ Of aninch. The first wood reducer 40 can be a miller, or other equivalentwood reducer. The miller particles are then milled into smallerparticles having a size between 150 mesh and 20 mesh in a second woodreducer 42. The second wood reducer 42 can be a miller or otherequivalent wood reducer. The sawdust waste and the impurities can have asize smaller than 150 mesh. The combined sawdust waste, impurities, andthe milled particles form a waste flour. The urea formaldehyde in thewaste board 34 is in a solid state, and therefore the wood reducingsteps also chop the urea formaldehyde into smaller particles of solidurea formaldehyde. The waste flour is stored in a holding accumulator 44until needed.

[0017] Alternately, the waste flour is created by chopping wood andsolid urea formaldehyde to create a mixture of chopped wood and choppedsolid urea formaldehyde.

[0018] The waste flour has a moisture content between 7-15%. A dryer 38removes moisture in the waste flour. After drying, the combined wasteflour preferably has a moisture content of less than one half of 1%. Themoisture content of the waste flour must be kept low. If the moisturecontent is too high, the moisture will boil away when the waste flour islater mixed with the thermoplastic 50, creating voids that weaken thecomposite board 72.

[0019] The dried waste flour is then added to a blender 48 for mixingwith other materials. Thermoplastic 50 is added to the blender 38 tobind and ecapsulate the waste flour. Preferably, the thermoplastic isvirgin high density polyethylene. However, the thermoplastic can also below density polyethylene, polypropylene, polyvinyl chloride, impactco-polymer polypropylene or styrene acrylonitril. The thermoplastic canalso be reground/recycled thermoplastic or a blend of virginthermoplastic and reground/recycled thermoplastic. One skilled in theart would know what thermoplastic to employ.

[0020] Lubricants are also added to the blender 48. Internal lubricants52 are added to improve the flow characteristics of the blendedmaterial, and external lubricants 54 are added to prevent sticking ofthe blended material during extrusion or molding 66. In one example, theinternal lubricant 52 is ethylene bis-steramide, and the externallubricant is zinc stearate or calcium stearate. However, any materialthat provides a lubricant function can be employed, and one skilled inthe art would know what lubricants to employ.

[0021] Mineral fillers 56 are also added to the blender 48. The mineralfillers 56 are very fine, combining with the mixture to improve theflexural modulus and stiffness of the composite board 72. The mineralfillers also fill in the voids between the waste flour particles.Preferably, talc (magnesium silicate) is the mineral filler.Alternately, calcium carbonate and aluminum tri-hydrate can also beemployed as the mineral filler. If the mineral filler 56 is aluminumtri-hydrate, the composite board 72 is flame retardant and has increasedcorrosion resistance.

[0022] A plasticizer 58 can be added to the blender 48 to improve thephysical properties or mechanical characteristics of the composite board72. If the thermoplastic 50 is polyvinyl chloride, a plasticizer 58 isneeded to provide these characteristics. In one example, the plasticizeris diocytl phthalate.

[0023] An ultraviolet absorber 60, a biocide 62, and a pigment 64 canalso be added to the mixture in the blender 48. The ultraviolet absorber60 is used to absorb ultraviolet light. In one example, the ultravioletabsorber 60 is Tinuvin 770 manufactured by Ciba. The biocide 62 isemployed to prevent rotting and to resist fungal attaches. In oneexample, the biocide 62 is Poly Alpha BN manufactured by Towa Chemicalor lonepure manufactured by Wells Plastics LTD. The pigment 64 isemployed to provide color. Titanium dioxide or zinc sulfide can beemployed as the pigment 64 to provide a white color. Red iron oxide canbe employed as the pigment 64 to provide a red color. Black iron oxideor carbon black can be employed as the pigment 64 to provide a blackcolor. Zinc ferrite can be employed as the pigment 64 to provide ayellow color. Manganese ferrite can be employed as the pigment 64 toprovide a brown color.

[0024] The waste flour, thermoplastic 50, internal lubricant 52,external lubricant 54, mineral filler 56, plasticizer 58, ultravioletabsorber 60, biocide 62, and pigment 64 are mixed in the blender 48 toform a homogenously blended material.

[0025] Preferably, the uniformly blended material includes approximately40-70% waste flour, approximately 30-50% thermoplastic 50, approximately1-3% lubricant 54, 56, approximately 3-12% mineral filler 56, andapproximately 0.05-3% plasticizer 58, ultraviolet absorber 60, biocide62, and pigment 64. In one example, the mixture includes 58% wasteflour, 31% high density polyethylene (thermoplastic), 8% talc (mineralfiller), 2% zinc stearate (external lubricant), and 1% ethylenebis-stearamide (internal lubricant).

[0026] The blended material is transferred to an extruder 66 and heatedto approximately 300-450° F. to melt the thermoplastic 50. The meltedmaterial is then extruded through a die 68 into a desired shape.Alternately, the blended material can be heated and formed into adesired shape by injection molding or compression molding. Thethermoplastic 50 in the mixture hardens and cools in a cooling tank 70to solidify the mixture and form the composite board 72. The hardenedcomposite board 72 is then cut or machined to a desired size and shapein a cutter or machine 74. The composite board 72 can also be runthrough a die to create texture on the surface of the composite board72. The composite board 72 can be coated 76 with polyvinyl chloride(PVC), melamine, metal, foil, impregnated paper, wood veneer, orpolyester. Finally, the composite board 72 is packaged 78 for shippingto a customer. The composite board 72 of the present invention can beused to make cabinets, molding, deck board, storage units, desks,building products, such as shingles, or any other product that usescomposite boards. The composite board 72 can also be used in interiorapplication or exterior applications.

[0027] The waste board 34 used to create the composite board 72 caninclude trace amount of impurities from the coating 32 of polyvinylchloride, melamine or metals applied on the waste board 34. Theimpurities can be aluminum, antimony, arsenic, barium, beryllium,cadmium, calcium, chromium, cobalt, copper, iron, lead, magnesium,manganese, mercury, molybdenum, nickel, selenium, silver, sodium,strontium, tin, vanadium or zinc. The impurities can also be benzene,carbon tetrachloride, chlorobenzene, chloroform, o-cresol, m-cresol,p-cresol, 1,4-dichlorobenzene, 1,2-dichloroethane, 1,1-dichoroehtylene,2,4-dinitrotoluene, hexachlorobenzene, hexachloro-1,3-butadiene,hexachloroethance, methyl ethyl ketone, nitrobenzene, pentachlorophenol,pyridine, tetrachloroethylene, trichloroethylene, 2,4,5-trichlorophenol,or 2,4,6-trichlorophenol.

[0028] There are several advantages to the composite board 72 of thepresent invention. For one, the waste board 34 is recycled and notthrown away, reducing the amount of material thrown into landfills. Thewaste board 34 is also not burned, reducing air pollution. Additionally,the composite board 72 has improved physical properties and is resistantto water absorption. The solid urea formaldehyde in the waste flourimproves tensile and flexural strength of the composite board 72. Thewaste flour and the solid particles of urea formaldehyde in thecomposite board 72 are encapsulated in the thermoplastic 50, reducingrotting of the composite board 72 and allowing the composite board 72 tobe used in exterior applications. The composite board 72 is not treatedto with chromated copper arsenate to prevent rotting, which is anenvironmental and health hazard.

[0029] The foregoing description is only exemplary of the principles ofthe invention. Many modifications and variations of the presentinvention are possible in light of the above teachings. The preferredembodiments of this invention have been disclosed, however, so that oneof ordinary skill in the art would recognize that certain modificationswould come within the scope of this invention. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described. For thatreason the following claims should be studied to determine the truescope and content of this invention.

What is claimed is:
 1. A method of making a composite materialcomprising the steps of: providing a plurality of wood particles and aplurality of solid urea formaldehyde particles to form a mixture; mixingsaid mixture with a bonding agent; and forming the composite material.2. The method as recited in claim 1 wherein said mixture includes 8-15%urea formaldehyde by weight.
 3. The method as recited in claim 1 whereinsaid plurality of wood particles and said plurality of solid ureaformaldehyde particles are integrated into a panel, and the step ofproviding said plurality of wood particles and said plurality of ureaformaldehyde particles includes chopping said panel into said pluralityof wood particles and said plurality of urea formaldehyde particles. 4.The method as recited in claim 1 wherein said plurality of woodparticles and said plurality of solid urea formaldehyde particles have asize between 150 mesh and 20 mesh.
 5. The method as recited in claim 1further including the step of drying said mixture.
 6. The method asrecited in claim 5 wherein the step of drying said mixture includesreducing a moisture content of said mixture to less than one half of 1%.7. The method as recited in claim 1 wherein said bonding agent is one ofhigh density polyethylene, low density polyethylene, polypropylene,polyvinyl chloride, impact co-polymer polypropylene, and styreneacrylonitril.
 8. The method as recited in claim 1, further including thestep of mixing said mixture with a first lubricant and a secondlubricant.
 9. The method as recited in claim 8 wherein said firstlubricant is zinc stearate and said second lubricant is ethylenebis-steramide.
 10. The method as recited in claim 1 further includingthe step of mixing said mixture with a plurality of mineral fillerparticles.
 11. The method as recited in claim 10 wherein said pluralityof filler particles is one of magnesium silicate, calcium carbonate, andaluminum tri-hydrate.
 12. The method as recited in claim 1 furtherincluding the step of mixing said mixture with a plasticizer.
 13. Themethod as recited in claim 1 further including the steps of mixing saidmixture with at least one of an ultraviolet absorber, a biocide, and apigment.
 14. The method as recited in claim 1 wherein the step offorming the composite material includes cooling said composite material.15. A method of making a composite material comprising the steps of:providing a panel including a plurality of wood particles and aplurality of solid urea formaldehyde particles; reducing said panel intosaid plurality of wood particles and said plurality of solid ureaformaldehyde particles to form a mixture; drying said mixture; mixingsaid mixture with a bonding agent, a first lubricant, a secondlubricant, and a mineral filler; and forming the composite material. 16.The method as recited in claim 15 wherein the step of reducing saidpanel includes chopping said panel into said plurality of wood particlesand said plurality a plurality of particles having a size between 150mesh and 20 mesh.
 17. The method as recited in claim 15 wherein saidbonding agent is high density polyethylene, said first lubricant is zincstearate, and said second lubricant is ethylene bis-steramide.
 18. Themethod as recited in claim 15 further including the step of mixing saidmixture with a plasticizer.
 19. The method as recited in claim 18wherein the composite material includes approximately 40-70% of saidplurality of wood particles and said plurality of solid ureaformaldehyde particles, approximately 30-50% of said bonding agent,approximately 1-3% of said first lubricant and said second lubricant,approximately 3-12% of said mineral filler, and approximately 0.05-3% ofsaid plasticizer.
 20. A composite material comprising: a plurality ofwood particles and a plurality of solid urea formaldehyde particles; anda bonding agent that bonds said plurality of wood particles and saidplurality of solid urea formaldehyde particles to form the compositematerial.
 21. The composite material as recited in claim 20 wherein thecomposite material includes approximately 50-70% of said plurality ofwood particles and said plurality of solid urea formaldehyde particles,approximately 30-50% of said bonding agent, approximately 1-3% of afirst lubricant and a second lubricant, approximately 3-12% of a mineralfiller, and approximately 0.05-3% of a plasticizer.